1. Field of the Invention
The present invention relates generally to a data storage device, and in particular, to a nanoscale digital data storage device for writing and reading data by mechanical contact.
2. Description of the Related Art
Thomas R. Albrecht, et. al. proposed a data storage system using a cantilever having a tip in U.S. Pat. No. 5,537,372 entitled “High Density Data Storage System with Topographic Contact Sensor”. In the data storage system, the tip physically contacts the surface of a storage medium and the medium has pits representing mechanically readable data on its surface. During a read operation, a change of the cantilever position is sensed and interpreted. If the surface of the medium is thermally transformable, data is written on the surface by heating the tip when the tip is brought into contact with the surface and thus forming pits on the surface. The tip is heated by a laser beam.
To improve the tip heating technique, a method has recently been proposed in which a single crystalline silicon cantilever is selectively doped with boron to provide a conductive path in an electrically resistive region near the tip. The tip is heated by flowing current in the conductive path.
These conventional data storage devices are equipped with a means for forcibly transforming or moving cantilevers perpendicularly to the storage medium. For writing a digital bit “1”, a corresponding cantilever contacts the medium surface, whereas for writing a digital bit “0”, a corresponding cantilever is spaced from the medium surface. Before the data writing, previous pits are eliminated by heating the overall medium surface to a high temperature which restores the surface shape due to surface tension.
A drawback of this writing mechanism is that the data storage device is very complex in structure to forcibly move or transform each cantilever. As more cantilevers are used, more moving means are required. The resulting high cost and low stability render the data storage device infeasible for mass production. Moreover, heating the overall surface of the storage medium before writing is not preferable in terms of energy efficiency.